The present invention relates to a magnet brush developing system for a copying machine and, more particularly, to a developer powder supply means for supplying developer powder to a magnet brush developing roller for developing an electrostatic laten image carried on a drum surface.
A magnet brush developing system is well known in the art, which includes a cylindrical magnet and a sleeve enclosing the cylindrical magnet. Either one of the cylindrical magnet and the sleeve is driven to rotate in a predetermined direction, whereby the developer powder is attracted to the sleeve surface and transported to the photo sensitive drum surface for developing purposes.
A typical magnet brush developing roller was disclosed in U.S. Pat. No. 3,040,704 entitled "APPARATUS FOR DEVELOPING ELECTROSTATIC PRINTING" issued on June 26, 1962, wherein a sleeve is driven to rotate around a stationary magnetic field producing means which is associated with a magnetic shunt means for reducing the magnetic field passing through a portion of the sleeve.
Another example of the magnet brush developing roller was disclosed in U.S. Pat. No. 3,909,258 entitled "ELECTROGRAPHIC DEVELOPMENT PROCESS" issued on Sept. 30, 1975, wherein a cylindrical magnet is driven to rotate within a stationary sleeve.
Generally, there are two types of developing roller. One type includes a stationary sleeve and a rotatable magnet, the magnet having an even number of magnetic poles. The other type includes a rotatable sleeve and a stationary magnet, the magnet having an odd number of magnetic poles.
The former type is suited for a developer powder including compounded toner and magnetically attractable material. That is, the former type is suited for the magnetically attractable toner such as disclosed in U.S. Pat. No. 3,909,258. The latter type is suited for a developer powder consisting of a mixture of the toner and magnetic particles such as disclosed in U.S. Pat. No. 3,040,704.
It has been proposed to provide a developer powder supply means for supplying the developer powder to the developing roller. The developer powder supply means of the conventional type is the same construction as the developing roller. The conventional developer powder supply means cannot supply the developer powder in preferred amount, and there is a possibility that the developer powder may become stiffened within the developer powder reservoir.